Multiplex drop channel system



Sept. 19, 1933. F, HALLDEN MULTIPLEX DROP CHANNEL SYSTEM Filed Nov. 9, 1931 I I I a I J l i I J l l I 1 L I FIG. 2

I I l I I I I L FIG.

INVENTOR FREDERICK C. HALLDEN BY A?" ATTORN Y Patented Sept. 19, 1933 1,927,704 I MULTIPLEX DROP CHANNEL SYSTEM Y Frederick G. Hallden, BelleroseiN. Y., .assignor I to International Communications 'Laboratories,, Inc., Newark, N.'J., a corporation of New York Application November 9, 1931. s rial No. 573,930

9 Claims. (onus- 5s) The present invention relates to printing telegraph systems and especially to synchronous multiplex systems. More particularly the invention pertains to drop channel repeaters, which are well known in the art.

Drop channel repeaters are used to provide channels of communication between terminal stations and intermediate stations. For example, a drop channel repeater might be installed at an intermediate point on a two-channel multiplex system and would provide in place of two com,- munication channelsbetween the terminal stations asingle channel between terminals and an additional channel'between each terminal and theintermediate station. Of course, such repeaters may be installedin systems of more than two channels; In the-common multiplex system, using drop channel repeaters, synchronism is maintained by-correcting the distributor at the drop channel or intermediate stationto the speed of the transmitting distributor at a terminal,

and, in turn, correcting the receiving distributor atthebther terminal to thedrop channel distributor. The maintenance of synchronism, 'or correction,- is achieved by'altering the phase displacement between the sending and receiving distributors by increasing or-de'creasing the speed of the receiving distributor under control of impulses generatedfrom'the line signals. Correcting means, as applied to drop channel distributorsare well explained inConnery Patents Nos.

1,599,514- and 1,679,852. I -It-is obvious that in a system, as above set forth,- failure ofa line section between adjacent stations causes a loss of synchronismgand causes all channel's of the-system to-be-inoperative. "Synchronism maybe're'stored by adjusting the drop channel distributor to operate at'a speed which is the mean of the transmitting dis tributor speed and the receiving distributor speed. However, when this is done manually a considerable period elapses before traffic can be resumed overthe re-established channel; In ac one section of the. lineto operate the distributor of the drop channel orintermediate station at a mean value of speed. This will permit maintenance of synchronism ,over the good line section. -'Referring tothe drawing? r Figure 1 illustrates two terminal stations 1 and 3 connected through the intermediate drop channel station 2. ,The broken lines showsome of the various traflic channels and the direction thereof possible in such a'system. These lines i are sumcient to illustrate, one. adaptation of the invention; and v I y Figure 2 shows-a detailed arrangement of the invention as used at the. intermediate; station. 2;

It is. to 'be noted thatythis invention isuseful with any of the well-known types of multiplex systems utilizing distributorseither. of the cam type, as disclosed in Connery 1,599,514, or-the rotary type which is alsoin common use.

= Referring now to Figure l, there is shown a 7 communication between stations; 1 and 3,;and 8Q drop channel repeater from station 1 to station 2 andfrom station 2 to station'3. Normally,

all channels are duplexed' 'sothat six vmessages may be transmitted simultaneously.

system with a single'drop channel repeater, it is to be noted that the invention, hereinafter dejscribed in detail, may beJVusedwith.othergmultiplechannel systems-and; may be utilized when more thanone intermediate,stationis provided y for operation with the terminals. p Referring .nowto Figure 2, there are shown the elements necessary, for practicingithe present in for channels of communication alsothrough the x While thisydrawing illustrates a two-channel vention in such detail onlyas is necessary forja Q5 trols tongue-6 so that positive or negativebattery. is applied to conductor '7, which, in turn, I

Linesignalsare I utilized to provide corrector action inthe; well.- known manner, a s, ShOWIlyfOl example, inLConnery- Patents 1,599,514- and. 1,679,852. Signals leads to the rotary distributor.

coming in; oyergline l6lcaus'e operation of relay 15 and apply positive ornegative battery, over tongue16'of relay'15 and conductor '7 to the re-" Q ceiving segmentsof the drop channel'distribu- .tor. Corrector relay 1 1 is operatediinthe usual manner through the co-ope'rationgofline signals land signals from the; correcting segmentsof thedistributor, as is well knownin thezart. ,Nor-

completeunderstanding thereof. Relay 15 .con-

mally, operation of. relay 11 causes a current'flow from battery through a resistance, such as 13, and through the corrector magnets 14 to ground, thus producing a magnetic field in the vicinity of the tines of the vibrating tuning fork, thereby damping the vibrations of the fork. This increases the frequency of the vibrations of the tuning fork, thereby speeding up the drop channel distributor and synchronizing it with the transmitting distributor at the terminal station.

In order that failure of the'line section 4 con-' necting stations 1 and 2 be ineffective to cause a loss of synchronism between stations 2 and 3,

the additional apparatus ofthe presentinvention is installed.

Two slow-release relays 8; and 9 are connecte d,

one in each contact lead of the receiving relay 6. Normal operating signals will maintain both these relays in their operated or open positions, as shown in Fig. 2, thereby'h'olding open the circuit to the biased slow-operating relay 10 which is common to both slow-releasing relays. The slow-operating relay 10 may be adjusted to require, say, five seconds current duration to op- 25 erate. In the unoperated position of slow-operating'relay 10, as shown in Fig. 2, the circuit from the contacts of corrector relay 11 to the corrector magnets-l4 is normal, current being supplied to corrector magnets 14 through 1500- ohm coil 13 when corrector relay 11 is operated, 1500- ohm coil 12 being on open circuit. When the line; section 4 fails, line 16 of Fig. 2 likewise fails and the tongue of receiving relay 15 will lie against either one of its contacts 6 and the corresponding slow-releasing relay 8 or 9 will release its armature and close the circuit to the slow-operating relay 10. 'When this circuit has been closed for'the predetermined time,

1' the slow-operating relay 10 will close a circuit to'the corrector magnets 14 through 3000 ohms resistances, 12'and 13 in series, thereby causing corrector magnets 14 to be less strongly energized, and cause thedrop channel distributor to rotate at the approximate mean rate of speed.

This condition will be maintained until signals are again received over line section 4Land likewise line 16,-which will operate receving relay 15 and, subsequently, the corresponding slowg i releasing relay 8 or 9, thereby restoring the biased slow-operating relay 10' to its, normal position' so' that the corrector circuit will again function normally.

- Although the invention has been shown'as applied to a particular type of telegraph system, it .is, of course, obvious to those versed in the art that it is equally applicable to other types of systems, and may be' used in any circuit where synchronism is to be maintained in a' corrected 7 station or stations upon the failure of the master correcting station or pace setting station asso- -ciated withthe corrected station or stations.

- The particular embodiment of the invention here-described contemplates the use of the fiveunit Baudot code, the'employment of automatic transmission by perforated tape, and the use of rotary distributors of the cam type. This invention, howevenmay be used to advantage inconnection with any other type of code, equal letter or unequal-letter, and with means of transmission other than by'tape, and is als suitable for use in connection with rotary distributors of the brush and segment' type- The 'mo'difications of systems other than that disclosed by-Connery above will. readily present themselves to those versed in the art.

remaining stations, said means being responsive toa failure of the line section from said first station forautomatically causing apparatus at the balance of said remaining stations to be driven in synchronism with-apparatus at said abovementioned one of the remaining stations.

2. In a signaling system, a plurality of stations, line sections for successively connecting said stations, means at a first of said stationsfor synchronizing apparatus at the remaining stations therewith, and relays at one of the remaining stations, said relays being responsive to an open conditionon the line section from said first station for causing apparatusat the balance of said remaining stations to be driven in synchronism with apparatus at one. of the remaining stations.

3.- In a signaling system, a plurality of stations, line. sections connecting .said stations,

means at a first of said stations for synchronizing apparatus at the remaining stations therewith, and means comprising-relay means atone of the remaining stations responsive to an open condition on the line section from said first station existing for a predetermined time in; terval for causing apparatus at the balance of said remaining stations to be drivenin synchro nism therewith. I p V 4. In a signaling system, a, plurality of stem:

tions; line sections connecting said stations, 7

means at a first of said stations for synchronizing apparatus at the remaining stations there with, and means comprising slow-release and slow-operate relays at one of the remainingsta tions responsive to a predetermined condition upon the line section from said first station eX-i isting for a predetermined time interval for caus' ing apparatus at the balanceof saidremaining.

stations to be driven in synchronism ;with 3D", 7

'paratus at the above-,enumeratedgoneof said.

remaining stations. 5. In a signaling system, a plurality of stations, line sections connectingsaid stations,

means'at a first of said stations for synchron'e izing, apparatusat the remaining stations therewith and means atone of the remaining stations responsive to the failure of the line section,

from said first station to transmit signalsior tions to bedriven in synchronism with appa ratus at the above-mentioned one of the res mainingstations. I p i 6. Ina signaling system, a plurality of sta tions, line sections connecting said stations, means at a first of said stations for synchronize ,ing apparatus of the remaining stationstheree with, a plurality of additional stationsconnected with one of said remaining stations,: said last mentioned station being adrop *channe'l station connecting said first station with said additional stations for synchronizing apparatus ,a'predetermined" time interval for causing ap-r.

paratus at the balance of said remaining sta thereat with the means at said first station, and

a series of electromagnetic means responsive to the failure of said drop channel station to receive signals from said first-mentioned station throughout a predetermined time interval for causing apparatus at the drop channel station to maintain apparatus at the additional stations in synchronism with the apparatus at said drop channel station.

7. In a signaling system, a plurality of stations, line sections connecting said stations,

means at a first of said stations for synchronizing apparatus of the remaining stations therewith, a plurality of additional stations con-'- nected with one of said remaining stations, said last mentioned station being a drop channel station connecting said first stations with said stations, means at thefirst of said stations for synchronizing the distributors at the remaining stations therewith, and relays at one of the remaining stations responsive to a predetermined condition of the line section from said first station to transfer the synchronization of the distributors at the balance of said remaining stations to the above-enumerated one ofthe re-;

maining stations.

9. In a signaling system, a transmitting station, a receiving station, an intermediate drop channelstation having a receiving relayprovided with marking and spacing contacts and adapted to receive signals fromsaid transmitting station, line sections connecting said sta tions, means at said transmitting station for synchronizing apparatus at the remaining stations therewith, and transfer means at said drop channel station, said means comprising a pair of slow release relays one of said pair being dis I posed in a circuit including said'marking contact, the other of said pair being disposed in a line section from said transmitting station for circuit including said spacing contact, either of said relays being responsive to a failure of the a predetermined time interval, to transfer the synchronization of the apparatus at the remaining stations to said drop channel station.

FREDERICK- G. HALLDEN. 

